Heat exchanger

ABSTRACT

A heat exchanger is provide, in which a fin member and a tube member are joined each other, wherein the fin member includes a solder wetting film layer containing copper, in at least a part of a surface of a fin substrate made of aluminum or an alloy mainly composed of aluminum, where the fin member and the tube member are joined each other, and the tube member includes a solder film layer made of solder containing tin, in at least a part of a surface of a tube substrate made of copper or an alloy mainly composed of copper, where the tube member and the fin member are joined each other, wherein the fin member and the tube member are joined each other, through a diffusion bonding of a copper component of the solder wetting film layer and a tin component of the solder film layer.

TECHNICAL FIELD

The present invention relates to a heat exchanger having a structure in which a fin member and a tube member are joined each other.

DESCRIPTION OF RELATED ART

A heat exchanger includes a structure in which a fin member and a tube member are joined each other. For example, in a case of the heat exchanger used as a radiator for cooling an engine of an automobile, the fin member, the tube member, and a tank member are combined, with essential parts of them joined each other. As a main joint part, there are a part between the tank member and the tube member, and a part between the fin member and the tube member, and generally such members are joined each other by soldering and brazing (patent document 1)

If the heat exchanger is classified, with the joint between the fin member and the tube member focused on, there are mainly two kinds such as the heat exchanger made of brass wherein the fin member and the tube member molded by using a plate material of brass (or a copper (Cu)-based alloy similar to brass) as a metal material, are joined each other by soldering of in-furnace heating at 300° C. or less, and the heat exchanger made of aluminum wherein the fin member and the tube member, molded by using a plate material of aluminum (Al: including not only pure Al but also an Al alloy, etc.), are joined each other by aluminum brazing of in-furnace heating at about 600° C.

The heat exchanger made of brass was used in most of the heat exchangers for automobiles before 1990. However, owing to a progress of the aluminum brazing technique and due to a problem of lead (Pb) involved in solder, the latter heat exchanger made of aluminum is used in most cases in recent years. However, when aluminum can not be used due to inconveniences such as corrosion in the tube member, the former heat exchanger made of brass is used even now. However, in a case of the heat exchanger made of brass, there is an unavoidable defect such as a heavy weight, compared with the latter heat exchanger made of aluminum.

Further, the heat exchanger made of all aluminum, using a solder joining technique is also proposed (patent document 2). As a main essential part of the all aluminum-made heat exchanger, the fin member and the tube member are made of aluminum by applying nickel (Ni) plating all over the surface of them, and after they are temporarily assembled, each part where the fin member and the tube member are brought into contact with each other is joined by soldering.

(Patent document 1)

Japanese Patent Laid Open Publication No. 2007-136490

(Patent document 2)

Japanese Patent Laid Open Publication No. 1985-102270

Generally, the aluminum brazing is apt to be more complicated in its process, thus incurring higher cost than soldering. Therefore, even in a case of the heat exchanger made of all aluminum, the soldering is preferably used for its joint.

However, a conventional technique involves a problem that it is extremely difficult to surely join the fin member and the tube member made of aluminum by soldering.

Further, in order to overcome both of a susceptibility to a corrosion, which is a defect when the heat exchanger is made of all aluminum, and a defect that total weight is increased, which is a defect when the heat exchanger is made of all brass, it is effective to use a method of making a the tube member using a copper-based material such as brass, and also making the fin member using aluminum. We study on this method, but in this case, there is a problem that it is extremely difficult to surely join a member made of aluminum and a member made of copper-based metal such as brass by plating according to the conventional technique.

Further, in order to realize excellent soldering to the member made of aluminum as described above, it can be considered to use a technique of using a flux having an activity strong enough to melt an oxide film (passivation film) on the surface of aluminum of this member. However, actually, there is a high possibility that a part near the joint part is remarkably damaged and deteriorated after soldering by use of such an extremely strong flux as described above, which is an undesirable defect from a viewpoint of durability and reliability of the joint part.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a heat exchanger having a structure in which a fin member made of aluminum or an alloy mainly composed of aluminum, and a tube member made of copper or an alloy mainly composed of copper, are joined each other satisfactorily, through a diffusion bonding of copper and tin.

According to an aspect of the present invention, a heat exchanger is provided, having a structure in which a fin member and a tube member are joined each other, wherein the fin member includes a solder wetting film layer containing copper, in at least a part of a surface of a fin substrate made of aluminum or an alloy mainly composed of aluminum where the fin member and the tube member are joined each other, and

the tube member includes a solder film layer made of solder containing tin, in at least a part of a surface of a tube substrate made of copper or an alloy mainly composed of copper where the tube member and the fin member are joined each other,

wherein the fin member and the tube member are joined each other, through a diffusion bonding of a copper component of the solder wetting film layer and a tin component of the solder film layer.

Further, according to other aspect of the present invention, a heat exchanger is provided, having a structure in which a fin member and a tube member are joined each other,

wherein the fin member includes a solder wetting film layer containing copper, in at least a part of a surface of a fin substrate made of aluminum or an alloy mainly composed of aluminum where the fin member and the tube member are joined each other, and

the tube member includes a solder film layer made of solder containing tin, in at least a part of a surface of a tube substrate made of copper or an alloy mainly composed of copper where the tube member and the fin member are joined each other,

wherein the fin member and the tube member are joined each other, through a diffusion bonding of a copper component of the solder wetting film layer and a tin component of the solder film layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a main essential part of an overall structure of a heat exchanger according to an embodiment of the present invention.

FIG. 2 is a view showing a fin substrate used in the heat exchanger according to a first embodiment of the present invention.

FIG. 3 is a view showing a tube substrate used in the heat exchanger according to the first embodiment of the present invention.

FIG. 4 is a view showing a tank substrate used in the heat exchanger according to the first embodiment of the present invention.

FIG. 5 is a front view showing a sample having a structure of the heat exchanger formed by joining the fin member and the tube member, and the tank member in the heat exchanger according to the first embodiment of the present invention.

FIG. 6 is a side view of a sample of joining the fin member, the tube member, and the tank member shown in FIG. 5.

FIG. 7 is a view showing a fin substrate used in the heat exchanger according to a second embodiment of the present invention.

FIG. 8 is a front view showing a sample of the structure of the heat exchanger wherein the fin member and the tube member are joined each other.

FIG. 9 is a view showing the structure of the fin member and the tube member, a heating temperature during joining, and a joint state indicated by a table form, according to an example 1 and a comparative example 1 of the present invention.

FIG. 10 is a view showing the structure of the fin member and the tube member, the heating temperature during joining, and the joint state indicated by a table form, according to the example 1 and the comparative example 1.

FIG. 11 is a view showing the structure of the fin member and the tube member, the heating temperature during joining, and the joint state indicated by a table form, according to an example 2 and a comparative example 2.

FIG. 12 is a view showing the structure of the fin member and the tube member, the heating temperature during joining, and the joint state indicated by a table form, according to an example 2 and a comparative example 2.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

A heat exchanger according to preferred embodiments of the present invention will be described hereinafter, with reference to the drawings.

As an overall structure common in heat exchangers according to the first and second embodiments of the present invention, as shown in FIG. 1, a fin member 1, a tube member 2, and a tank member 3 are provided, as essential parts thereof.

In the heat exchanger having this structure, the fin member 1 is formed in a wave shape. Such a wave shape contributes to increasing a substantial surface area of the fin member 1, and also contributes to performing efficient heat exchange with outer air in a space 15 formed between the tube member and the fin member 1. Accordingly, when a refrigerant (high-temperature refrigerant) such as cooling water 4 is passed through the tube member 2, heat held by the cooling water 4 is transmitted to the tube member 2, then passed out, and further transmitted to the fin member 1 brought into contact with the tube member 2. Then, the heat transmitted to the tube member 2 and the fin member 1 is discharged into the outer air (low-temperature refrigerant) flowing through the space 15. Thus, the efficient heat exchange is performed in this heat exchanger.

Further, in this heat exchanger, the fin member 1 and the tube member 2 are surely joined each other by a solder joining technique according to an embodiment of the present invention.

Note that the fin member may be joined not to an outer face of the tube member but to an inner face of the tube member. Further, a direction of joining the fin member to the tube member may be a peripheral direction or an axial direction of the tube member. Further, the fin member may be continuously joined to the tube member or may be joined thereto discontinuously.

The Heat Exchanger According to a First Embodiment

In the heat exchanger according to the first embodiment, the fin member 1 is formed by folding and bending a fin plate material 9, an example of which is shown in FIG. 2, into a wave shape, and is disposed in a state of being interposed between adjacent two tube members 2, 2, and each part of the fin member 1 brought into contact with the tube member 2 is surely joined to the tube member 2. Further, the fin member 1 is disposed in a state of being interposed between right and left tank members 3. The fin member 1 and the tank member 3 may be joined each other or may be simply set in contact with each other mechanically.

The fin plate material 9 has a solder wetting film layer 5 containing copper (Cu), on approximately the whole surface or at least in a part of the fin substrate 6 made of aluminum (Al) or an alloy mainly composed of aluminum (Al) where the fin member 1 and the tube member 2 are joined each other.

According to a preferable numerical aspect, a thickness of the solder wetting film layer 5 is set to 5 nm or more and 400 nm or less, and further preferably set to 10 nm or more and 400 nm or less.

This is because if the thickness is less than 10 nm, it is highly possibly difficult to obtain solder wettability for obtaining a satisfactory joint (if the thickness is less than 5 nm, it is further remarkably difficult to obtain solder wettability), and also this is because if the thickness is beyond 400 nm, a manufacturing cost is highly possibly increased, due to a technical factor such that a time and a material are required for forming such a thick layer.

Here, as schematically shown in FIG. 2, it is a preferable aspect that the solder wetting film layer 5 has a two-layer lamination structure of a underlayer 7 made of niobium (Nb) and chromium (Cr), and a surface layer 8 made of an alloy mainly composed of copper (Cu) and added with at least one kind of metal of nickel (Ni) and zinc (Zn), provided on the surface of the underlayer 7.

With such a two-layer lamination structure, separation between the solder in a heated and melted state, and aluminum (Al) can be prevented.

In the solder wetting film layer 5 having the two-layer lamination structure, it is preferable that the underlayer (adhesive layer) 7 made of niobium or chromium is a sputter film made of niobium or chromium, with an internal residual stress of this sputter film set as a compressive stress or zero stress, and the surface layer (bonding layer) 8 mainly composed of copper and added with at least one kind of metal of nickel and zinc is the sputter film. Further, it is preferable to set an oxygen amount contained in the underlayer (adhesive layer) 7 and the surface layer (bonding layer) 8 to be extremely small, and when the underlayer (adhesive layer) 7 and the surface layer (bonding layer) 8 are formed by sputtering, film formation is performed in a film forming atmosphere in which oxygen is removed as much as possible. Further, the thickness of the underlayer (adhesive layer) 7 is set to 10 nm or more and the thickness of the surface layer (bonding layer) 8 is set to 15 nm or more.

Aluminum or an aluminum-based alloy has an oxide film (passivation film) on an outermost surface, and therefore originally they are materials difficult to plate and the materials difficult to solder. However, by forming the underlayer (adhesive layer) 7 and the surface layer (bonding layer) 8 formed of the aforementioned sputter film, excellent solder wettability and bonding strength to soldering can be given to the surface of the fin substrate 6 made of aluminum or an aluminum-based alloy having the passivation film formed on the outermost surface, even if not removing the passivation film that exists on the outermost surface of the fin substrate 6 through acid pickling.

The tube member 2 is obtained by molding a tube plate material 10 shown in FIG. 3 into a pipe shape having, for example, a flat elliptic or rectangular sectional face, with a solder film layer 12 formed on its surface disposed outside. The tube member 2 is provided so as to be bridged between the right and left tank members 3, and serves as a conduit for guiding the refrigerant such as cooling water 4 from the tank member 3 of one side to the tank member 3 of the other side.

The tube plate material 10 includes the solder film layer 12 made of solder containing tin (Sn) on the whole surface or in at least a part of the tube substrate 11 made of metal containing copper or mainly composed of copper such as brass where the tube member 1 and the fin member 2 are joined each other.

According to a preferable numerical aspect, a thickness of the solder film layer 12 is set to 3 μm or more and 100 μm or less.

This is because it is highly possibly difficult to obtain a satisfactory joint if the film thickness is less than 3 μm, and also there is a high possibility that if the thickness is beyond 100 μm, the solder film layer 12 itself is easily peeled-off after joint or crack is easily generated, and also there is a high possibility that a material cost is increased for forming the thick solder film layer 12.

Further, according to a preferable aspect, it is also possible to make the solder film layer 12 made of pure tin, and not allow lead (Pb) and cadmium (Cd), etc, to be contained in the component of the whole body of the solder film layer 12. Thus, the joint is surely achieved by so-called lead-free soldering.

Further, according to a preferable numerical aspect, when the solder film layer 12 is made of pure tin, the thickness is set to 3 μm or more and 30 μm or less.

This is because when the thickness is made to be excessively thin like less than 3 μm or when the thickness is made to be excessively thick like more than 30 μm, there is a high possibility that the sure joint can not be achieved. Further specifically, this is because although satisfactory diffusion bonding is realized by diffusion of copper of the solder wetting film layer 5 toward pure tin of the film layer 12, at this time, if the film layer 12 made of pure tin is excessively thick, a sufficient diffusion is not carried out, and the satisfactory joint can not be achieved, and reversely when the film layer 12 is excessively thin, a function of securing wettability during joint can not be sufficiently exhibited, and the satisfactory joint can not be achieved.

Further, particularly when the thickness of the solder film layer 12 made of pure tin is beyond 30 μm, joint is made by diffusion of the copper of the surface layer of the fin member 1 during heating in a soldering process for joint. There is also a possibility that inconvenience occurs, such that a copper concentration is decreased.

The tank member 3 is constituted, so that the refrigerant such as high temperature cooling water 4 sent from, for example, an engine is distributed and supplied to the tube member 2 by the tank member 3 of one side, and the cooling water 4 passed through the tube member 2 and cooled is recovered and returned to the engine by the tank member 3 of the other side.

As shown in FIG. 4, for example in the same way as the case of the tube plate material 10, the tank plate material 13 can be used, with the solder film layer 12 made of solder containing tin provided on the surface of the tank substrate 14 made of metal containing copper or mainly composed of copper. Alternatively, when there is no necessity for being joined to the fin member 1, the solder film layer 12 on the surface of the tank plate material 13 can also be omitted, provided that a sure (with high water tightness) joint between the fin member 1 and the tube member 2 made of copper-based metal is secured by general soldering, etc. Alternatively, the tank member 3 may also be made of a material other than metal, provided that the joint capable of securing the water tightness against the tube member 2 is achieved.

As described above, the fin member 1, the tube member 2, and the tank member 3 are assembled, and a contact part of them are joined each other in each essential part, to thereby constitute the main essential part of the heat exchanger (a connection structure of the heat exchanger is simulated) according to the first embodiment of the present invention, as shown in FIG. 5 and FIG. 6. Here, in the structure of the heat exchanger shown in FIG. 5 and FIG. 6, a sample of the connection structure is shown, and therefore the tube member 2 is not formed into a flat tube-like shape, but substantially formed into a shape obtained by cutting the flat tube into about half.

The heat exchanger thus formed has a solder wetting film layer 5 containing copper in at least a part of the surface of the fin substrate 6 made of aluminum or an alloy mainly composed of aluminum where the fin member 1 and the tube member 2 are joined each other; and has the solder film layer 12 made of solder containing tin in at least a part of the surface of the tube substrate 11 made of metal containing copper and mainly composed of copper where the tube member 1 and the fin member 1 are joined each other, so that the fin member 1 and the tube member 2 are joined each other through a diffusion bonding (diffusion joining) of the copper component of the solder wetting film layer 5 and the tin component of the solder film layer 12.

In the heat exchanger of the first embodiment formed as described above, the fin member 1 and the tube member 2 are temporarily assembled and thereafter heat treatment is applied thereto, to thereby cause mutual heat diffusion of the copper component of the melted solder wetting film layer 5 or particularly the surface layer 8 in the structure of the first aspect (the copper component can be diffused to outside from the film by being melted; the same thing can be said hereinafter), and the tin component of the melted solder film layer 12 on the surface of the tube member 2. Then, a metal diffusion bonding is thereby formed, and as a result, satisfactory solder joint can be surely obtained.

As described above, according to the heat exchanger of the first embodiment, a satisfactory joint can be surely realized, between the fin member 1 made of aluminum or an alloy mainly composed of aluminum, and the tube member 2 made of copper or a copper-based alloy, without using a flux with excessively strong activity, and without using a joint method which is complicated like aluminum brazing and incurs a high cost.

Further, the fin member 1 is made of aluminum or the alloy mainly composed of aluminum, and the tube member 2 is made of the copper-based alloy such as brass. Therefore, both decrease of a weight and improvement of a corrosion resistance of the heat exchanger manufactured by using the aforementioned fin member 1 and the tube member 2, is achieved.

Further, when the solder film layer 12 made of pure tin is used, a so-called Pb-free solder joint is possible, and therefore manufacture of an environmentally-friendly heat exchanger is realized.

The Heat Exchanger According to a Second Embodiment

In the heat exchanger according to the second embodiment, the fin member 1 as shown in FIG. 7 is used. Namely, the fin member 1 is formed by further adding the solder film layer 12 to the outermost surface of the fin plate material 9 of the first embodiment, and folding and bending this fin plate material 9 into a prescribed wave shape. The fin member 1 is disposed in such a manner as being sandwiched between the adjacent two tube members 2 and 2, so that each part where the tube member 2 and the fin member 1 are brought into contact with each other, is surely joined each other. Moreover, the fin member 1 is disposed in such a manner as being sandwiched between right and left tank members 3. The fin member 1 and the tank member 3 may be joined each other or may be set in a state of simply being brought into contact with each other mechanically.

Further specifically, the fin member 1 has the solder wetting film layer 5 containing copper, on approximately the whole surface of the fin substrate 6 made of aluminum or mainly composed of aluminum, or at least in part of the surface thereof where the fin member 1 and the tube member 2 are joined each other.

According to a preferable numerical aspect, the thickness of the solder wetting film layer 5 is set to 10 nm or more and 400 nm or less, for the same reason described in the first embodiment.

According to a preferable aspect of the present invention, as schematically shown in FIG. 7, here, the solder wetting film layer 5 has a two-layer lamination structure of the underlayer 7 made of niobium or chromium, and the surface layer 8 made of an alloy mainly composed of copper and added with at least one kind of metal of nickel and zinc, provided on the surface of the underlayer 7, also for the same reason as described in the first embodiment.

Further, in the solder wetting film layer 5 having the aforementioned two-layer lamination structure, preferably, the underlayer (adhesive layer) 7 made of niobium or chromium, is the sputter film made of niobium or chromium, and the internal residual stress of the sputter film is set as the compressive stress or the zero stress, and the surface layer (bonding layer) 8 mainly composed of copper and added with at least one kind of metal of nickel and zinc, is the sputter film. Further, it is preferable to set an oxygen amount contained in the underlayer (adhesive layer) 7 and the surface layer (bonding layer) 8 to be extremely small, and when the underlayer (adhesive layer) 7 and the surface layer (bonding layer) 8 are formed by sputtering, film formation is performed in a film forming atmosphere in which oxygen is removed as much as possible. Further, the thickness of the underlayer (adhesive layer) 7 is set to 10 nm or more and the thickness of the surface layer (bonding layer) 8 is set to 15 nm or more. Such a structure is preferable, also for the same reason as described in the first embodiment.

The solder film layer 12 made of solder containing tin, is provided on the surface of the solder wetting film layer 5. According to a preferable numerical aspect, the thickness of the solder film layer 12 is set to 3 μm or more and 100 μm or less.

This is because it is highly possibly difficult to obtain a satisfactory joint if the film thickness is less than 3 μm, and also there is a high possibility that if the thickness is beyond 100 μm, the solder film layer 12 itself is easily peeled-off after joint or crack is easily generated, and also there is a high possibility that a material cost is increased for forming the thick solder film layer 12.

Further according to a preferable aspect, it is also possible to make the solder film layer 12 made of pure tin, and not allow lead (Pb) and cadmium (Cd), etc, to be contained in the component of the whole body of the solder film layer 12. Thus, the joint is surely achieved by so-called lead-free soldering.

When the solder film layer 12 is made of pure tin, it is a preferable numerical aspect that the thickness is set to 3 μm or more and 30 μm or less. This is because there is a high possibility that sure joint can not be obtained, when the thickness is set to be excessively thin like less than 3 μm, or is set to be excessively thick like beyond 30 μm. Further, particularly when the thickness of the solder film layer 12 made of pure tin is beyond 30 μm, joint is made by diffusion of the copper on the surface layer of the fin member 1 during heating in the soldering process for joint. There is a possibility that inconvenience occurs, such that a copper concentration is decreased.

Although not shown, the tube member 2 is formed by molding the tube plate material 10 into a flat pipe shape having, for example, an elliptic or rectangular sectional face, wherein the tube plate material 10 is made of only the tube substrate 11, which is made of metal containing copper or mainly composed of copper such as brass. Namely, the tube plate material of the second embodiment is obtained by omitting the solder film layer 12 from the tube plate material 10 as shown in FIG. 3. The tube member 2 is provided so as to be bridged between the right and left tank members 3 and 3, serving as a conduit for guiding the refrigerant such as cooling water 4 from the tank member 3 of one side to the tank member 3 of the other side.

The tank member 3 is constituted, so that the refrigerant such as high temperature cooling water 4 sent from, for example, an engine is distributed and supplied to the tube member 2 by the tank member 3 of one side, and the cooling water 4 passed through the tube member 2 and cooled is recovered and returned to the engine by the tank member 3 of the other side.

The tank plate material 13 can be used, having the solder film layer 12 made of solder containing tin provided on the surface of the tank substrate 14 made of an alloy containing copper or mainly composed of copper. Alternatively, when there is no necessity for being joined to the fin member 1, the solder film layer 12 on the surface of the tank plate material 13 can also be omitted, provided that a sure (with high water tightness) joint between the fin member 1 and the tube member 2 made of copper-based metal is secured by general soldering, etc. Alternatively, the tank member 3 may also be made of a material other than metal, provided that the water tightness against the tube member 2 is secured by jointing.

As described above, the fin member 1, the tube member 2, and the tank member 3 are temporarily assembled, and thereafter a contact part of them are joined each other in each essential part, to thereby constitute the main essential part of the heat exchanger (a connection structure of the heat exchanger is simulated) according to the second embodiment of the present invention.

Namely, in the heat exchanger according to the second embodiment, the solder wetting film layer 5 containing copper and the solder film layer 12 further formed on the surface of the solder wetting film layer 5 are provided at least in a part of the surface of the fin substrate 6 made of aluminum or an alloy mainly composed of aluminum where the fin member 1 is brought into contact with the tube member 2. Further, the tube member 2 is formed by molding the tube plate material 10 into a tube shape, wherein the tube substrate 11 itself made of copper or mainly composed of copper is used as the tube plate material 10, and the fin member 1 and the tube member 2 are joined each other, mainly through the diffusion bonding of the copper component of the tube member 2 and the tin component of the solder film layer 12.

In the heat exchanger according to the second embodiment, the fin member 1 and the tube member 2 are temporarily assembled, and thereafter heat treatment is applied thereto, and heat diffusion of copper and tin is caused in a melted solder between the fin member 1 and the tube member 2, to thereby form a metal diffusion bonding, and as a result satisfactory solder joint between the fin member 1 and the tube member 2 can be surely achieved.

As described above, according to the heat exchanger of the first embodiment, the satisfactory joint can be surely realized, between the fin member 1 made of aluminum or an alloy mainly composed of aluminum, and the tube member 2 made of copper or a copper-based alloy, without using a flux with excessively strong activity, and without using a joint method such as aluminum brazing which is complicated and requires a high cost.

Further, the fin member 1 can be made of aluminum or the alloy mainly composed of aluminum, and the tube member 2 can be made of the copper-based alloy such as brass. Therefore, both decrease of a weight and improvement of the corrosion resistance of the heat exchanger manufactured by using the aforementioned fin member 1 and the tube member 2, is achieved.

Further, when the solder film layer 12 made of pure tin is used, a so-called Pb-free solder joint is also possible, and therefore manufacture of the environmentally-friendly heat exchanger is realized.

Examples

The fin member 1, tube member 2, and tank member 3 described in the aforementioned embodiments were prepared, and a trial model was manufactured by joining these members, to thereby evaluate and examine the joint.

Example 1

According to the first embodiment, as example 1, the trial model of the heat exchanger having the structure as shown in FIG. 5 and FIG. 6 was manufactured and its joint state was evaluated.

First, the fin member 9 having the structure as shown in FIG. 2, the tube plate material 10 having the structure as shown in FIG. 3, and the tank member 13 having the structure as shown in FIG. 4 were manufactured.

As the fin substrate 6, being the substrate of the fin plate material 9, a hard material of A5052, being an Al—Mg alloy (Al—Mg based alloy defined in JIS, containing 2.2 to 2.8 wt % of Mg) having thickness of t=50 μm, width of W1=16 mm, and length of 40 mm, was used.

As the tube substrate 11, being the substrate of the tube plate material 10, a brass material having a composition of Cu—35 wt % Zn, and having thickness of 230 μm, width W2=20 mm, and length of 80 mm, was used.

Also, as the tank substrate 14, being the substrate of the tank plate material 13, the brass material which is the same as the material of the tube plate material 10, and having thickness of 500 μm, width W3=30 mm, and length (height) H of 60 mm, was used.

Then, the solder wetting film layer 5 (underlayer 7 and the surface layer 8) as described in the first embodiment, was formed on the surface of the fin substrate 6 by sputtering, and the solder film layer 12 was formed on the surface of the tube substrate 11 and the tank substrate 14, respectively.

Further, these substrates are molded into prescribed shapes, to thereby manufacture the fin member 1, the tube member 2, and the tank member 3, then after such members are temporarily assembled, heat treatment is applied thereto, to thereby join essential parts by soldering, and the trial model of the heat exchanger having the structure as shown in FIG. 5 and FIG. 6 was manufactured.

As the underlayer 7 in the solder wetting film layer 5 of the fin member 1, there are two kinds of layers made of niobium (Nb) (samples 1 to 21 of FIG. 9), and the layer made of chromium (Cr) (samples 22 to 41 of FIG. 10). However, as the surface layer 8 combined with the aforementioned two kinds of underlayers 7, the layer made of copper (Cu)—20 wt % nickel (Ni) was used in both cases. The thickness of the underlayer 7 was set to 20 nm, and the thickness of the surface layer 8 was set to 60 nm.

A wave-shaped pitch D1 of the fin member 1 shown in FIG. 5 was set to 30 mm. Further, total length D2 of the tube member 2 and the tank member 3 assembled to both ends of the tube member 2 was set to 60 mm.

Then, three kinds of the tube members 2, with the solder film layer 12 made of Sn, made of Sn—37 wt % Pb, and made of Sn—3 wt % Bi (bismuth), were prepared for the sample of the two kinds of fin members 1, and heat treatment is applied thereto, to thereby join the fin members 1 and the tube members 2 each other.

As a forming method of the solder film layer 12 on the surface of the tube member 2, two kinds of methods were tried, such as an electric plating method and a hot dipping method.

Then, the fin member 1, the tube member 2, and the tank member 3 were joined each other by heat treatment, to thereby manufacture the trial model of the heat exchanger having the structure as shown in FIG. 5 and FIG. 6.

More specifically, the fin member 1, the tube member 2, and the tank member 3 were temporarily assembled into a prescribed structure, and thereafter RMA type (model number; HS-722, by HOZAN Inc.) with low activity as flux was applied thereto, to thereby perform joint by heat treatment for 3 seconds at 200° C. to 260° C., and a joint state of the fin member 1 and the tube member 2 was evaluated.

Regarding the evaluation method of the joint state between the fin member 1 and the tube member 2 immediately after joint by heat treatment, the evaluation method in a quality management/inspection of this kind of heat exchanger was used. Namely, absolutely no joint state visually is judged to be “without joint”, and a state, in which the fin member 1 and the tube member 2 are easily separated from each other when a load is added thereto even in a state of joint, is judged to be “failure”, and a state, in which the fin member 1 and the tube member 2 are not easily separated from each other, is judged to be “excellent”. Further regarding the sample judged to be “excellent”, a salt water spray test using salt water at 35° C. containing 5.0% salt was performed for 96 hours, as an environmental test. Then, regarding the joint state after performing the salt water spray test, in the same way as the case of judgment immediately after joint, the state, in which the fin member 1 and the tube member 2 were easily separated from each other, was judged to be “failure”, and the state, in which the fin member 1 and the tube member 2 were not easily separated from each other, was judged to be “excellent”.

A judgment (evaluation) result of the joint of samples 1 to 41 according to example 1 will be described hereinafter, in further detail.

FIG. 9 shows the result, in a case that the underlayer 7 of the fin member 1 is made of Nb, and in a case that the surface layer 8 is made of Cu—20 wt % Ni.

As shown in FIG. 9, in the samples No. 1 to 21 in which niobium (Nb) was selected as the material of the solder wetting film layer 5 of the fin member 1, approximately excellent joint was achieved. Meanwhile, in the samples No. 1 to No. 9, pure tin was selected as the material of the solder film layer 12 of the tube member 2, and in the sample No. 1 of comparative example 1, the thickness of the solder film layer 12 was 1.5 μm and excessively thin, and therefore the state of this sample was judged to be “without joint”.

Further, in the sample No. 2 of the comparative example 1, the thickness of the solder film layer 12 was 2 μm and very thin, and therefore it is so judged that the joint immediately after heat treatment was “excellent”, but the joint after performing the salt water spray test was “failure”. Reversely, in the sample No. 8 of the comparative example 1, the thickness of the solder film layer 12 was 40 μm and excessively thick, and therefore the joint immediately after heat treatment was judged to be “failure”.

Thus, generation of the failure of the joint due to thickness of the solder film layer 12, which is thin or thick, has the same tendency in both cases of a case of the sample No. 10 to No. 18 in which Sn—37 wt % Pb is selected as the material of the solder film layer 12, and a case of the sample No. 19 to No. 21 in which Sn—3 wt % Bi is selected as the material of the solder film layer 12. Namely, in the sample No. 10 and sample No. 11 of the comparative example 1, the thickness was set thin to 1.5 μm and 2 μm, and therefore the joint immediately after heat treatment was “excellent”, but the joint after performing the salt water spray test was “failure”. Reversely, in the sample No. 17 of the comparative example 1 in which the thickness was set excessively thick to 120 μm, the joint immediately after heat treatment was “failure”.

From the result as described above, it was confirmed that the thickness of the solder film layer 12 was desirably set to 3 μm or more and 100 μm or less. Also particularly it was confirmed that the film thickness was desirably set to 3 μm or more and 30 μm or less when pure tin was used as the solder film layer 12.

Further, when the thickness of the solder film layer 12 was set within a range of the above-described numerical aspect, it was confirmed that excellent joint could be achieved, irrespective of the forming method of the solder film layer 12, namely in either case of the electroplating method or the hot dipping method.

FIG. 10 shows the result of a case in which Cr is selected to be the material of the underlayer 7 of the fin member 1, and also Cu—20 wt % Ni is selected to be the material of the surface layer 8.

In this case also, approximately the same result was obtained as the case in which Nb was selected to be the material of the underlayer 7. However, in this case, regarding the sample No. 31 in which the thickness of the solder film layer 12 made of Sn—37 wt % Pb was set to 1.5 μm, “failure” was already shown immediately after heat treatment, unlike the above-described sample No. 11. However, in each case, it was confirmed from this result, that if the thickness of the solder film layer 12 was excessively thin like less than 3 μm, the excellent joint could not be achieved.

Example 2

According to second embodiment, as example 2, the trial model of the heat exchanger having the structure as shown in FIG. 8, was manufactured and its joint state was evaluated.

First, the fin plate material 9 having the structure as shown in FIG. 7, the tube plate material 10 (not shown), and the tank plate material 13 having the structure as shown in FIG. 4, were manufactured.

As the fin substrate 6, being the substrate of the fin plate material 9, a hard material of A3004, being an Al—Mn alloy (Al—Mn based alloy defined in JIS, containing 1.0 to 1.5 wt % of Mn) having thickness of t=60 μm, and width of W1=16 mm, was used.

As the tube substrate 11, being the substrate of the tube plate material 10, a brass material having a composition of Cu—35 wt % Zn, thickness of 230 μm, width W2=20 mm, and length of 40 mm, was used.

Also, as the tank substrate 14, being the substrate of the tank plate material 13, the brass material which was the same as the material of the tube plate material 10, and having thickness of 500 μm, width W3=30 mm, length of 80 mm, and height of 60 mm, was used.

Then, the solder wetting film layer 5 (underlayer 7 and the surface layer 8) as described in the second embodiment, was formed on the surface of the fin substrate 6 by sputtering, and the solder film layer 12 was further formed thereon, and the fin substrate 6 thus formed was molded into a prescribed shape, to thereby manufacture the fin member 1.

Further, the tube substrate 11 was used as it is, and molding process was applied thereto, to thereby manufacture the tube member 2.

Moreover, the solder film layer 12 was provided on the surface of the tank substrate 14, and molding treatment was applied thereto, to thereby manufacture the tank member 3.

Then, the fin member 1, the tube member 2, and the tank member 3 were temporarily assembled, and thereafter heat treatment was applied thereto, and the essential parts were joined each other by soldering, to thereby manufacture the trial model of the heat exchanger having the structure as shown in FIG. 8.

As the underlayer 7 in the solder wetting film layer 5 of the fin member 1, there are two kinds of layer made of niobium (Nb) (samples 1 to 24 of FIG. 11), and the layer made of chromium (Cr) (samples 25 to 48 of FIG. 12). However, as the surface layer 8 combined with the aforementioned two kinds of underlayers 7, the layer made of Cu—20 wt % Ni was used in both cases. The thickness of the underlayer 7 was set to 20 nm, and the thickness of the surface layer 8 was set to 60 nm.

Further, the solder film layer 12 was formed on the surface of the solder wetting film layer 5. Then, three kinds of the solder film layers 12, such as the solder film layer 12 made of Sn, made of Sn—37 wt % Pb, and made of Sn—3 wt % Bi, were prepared.

As the forming method of the solder film layer 12, two methods were tried in the samples No. 1 to No. 48 of the example 2 (including comparative example 2), such as the electroplating method without cathodic degrease as preprocessing, and the electroplating method with cathodic degrease as preprocessing. The cathodic degrease was carried out by using a sodium hydroxide solution at temperature of 50° C., with the sample set as a cathode, and under a condition that a current of 1.7 A/dm² flows. Although the hot dipping method was also tried, excellent solder plating was not achieved.

The fin member 1, the tube member 2, and the tank member 3 thus manufactured were temporarily assembled into prescribed structures, and they were joined by soldering by applying heat treatment thereto, to thereby obtain the trial model of the heat exchanged having the structure as shown in FIG. 8.

More specifically, the fin member 1, the tube member 2, and the tank member 3 were temporarily assembled into prescribed structures, and thereafter RMA type (model number; HS-722, by HOZAN Inc.) with low activity as flux was applied thereto, to thereby perform joint by heat treatment for 3 seconds at 200° C. to 260° C., and a joint state thereof was evaluated.

Regarding the evaluation method of the joint state between the fin member 1 and the tube member 2 after joint by heat treatment, in the same way as the case of the example 1, the evaluation method in a quality management/inspection of this kind of heat exchanger was used. Namely, absolutely no joint state visually is judged to be “without joint”, and a state, in which the fin member 1 and the tube member 2 are easily separated from each other when a load is added thereto even in a state of joint, is judged to be “failure”, and a state, in which the fin member 1 and the tube member 2 are not easily separated from each other, is judged to be “excellent”. Further regarding the sample judged to be “excellent”, a salt water spray test using salt water at 35° C. containing 5.0% salt was performed for 96 hours, as an environmental test. Then, regarding the joint state after performing the salt water spray test, in the same way as the case of judgment immediately after joint, the state, in which the fin member 1 and the tube member 2 were easily separated from each other, was judged to be “failure”, and the state, in which the fin member 1 and the tube member 2 were not easily separated from each other, was judged to be “excellent”.

A judgment (evaluation) result of the joint of samples 1 to 48 according to example 2 will be described hereinafter, in further detail.

FIG. 11 shows the result, in a case that the underlayer 7 of the fin member 1 is made of Nb, and in a case that the surface layer 8 is made of Cu—20 wt % Ni.

In the samples No. 1 to No. 24 in which niobium (Nb) was selected as the material of the underlayer 7 of the fin member 1, approximately excellent joint was achieved regarding the samples in which no cathodic degrease was carried out before performing electroplating of the solder film layer 12 (samples of “without cathodic degrease” in FIG. 11). The result was examined in further detail. In samples No. 1 to No. 10, pure tin was selected as the material of the solder film layer 12 of the tube member 2, and in the sample No. 1 of the comparative example 2, the thickness of the solder film layer 12 was 1.5 μm and excessively thin. Therefore the joint was judged to be “without joint”. Further, in the sample No. 2 of the comparative example 2, the thickness of the solder film layer 12 was 2 μm and thin. Therefore although the joint immediately after heat treatment was judged to be “excellent”, the joint after salt water spray test was judged to be “failure”. Moreover, in the sample No. 7, the thickness of the solder film layer 12 was 40 μm and thick. Therefore the joint immediately after heat treatment was judged to be “failure”.

Thus, the generation of the failure of the joint due to thickness of the solder film layer 12, which is thin or thick, has the same tendency in both cases of a case of the sample No. 11 to No. 21 in which Sn—37 wt % Pb is selected as the material of the solder film layer 12, and a case of the sample No. 22 to No. 24 in which Sn—3 wt % Bi is selected as the material of the solder film layer 12. However, in these cases, a suitable thickness for achieving the excellent joint was 3 μm or more and 100 μm or less. From such a result, it was confirmed that the thickness of the solder film layer 12 was desirably set to at least 3 μm or more and 100 μm or less, and particularly in a case of the solder film layer 12 made of pure tin, the film thickness was desirably set to 3 μm or more and 30 μm or less.

Further, when the cathodic degrease was carried out as the preprocessing of the electroplating (samples No. 8 to No. 10, No. 19 to No. 21 of the “with cathodic degrease” in FIG. 11), all of the samples were judged to be “without joint”, irrespective of the thickness.

From this fact, it was found that when the solder film layer 12 was formed by the electroplating method, on the surface of the solder wetting film layer 5 made of niobium (Nb), it is one of the conditions for achieving the excellent joint, to perform electroplating of the solder film layer 12 in a state of not carrying out the cathodic decrease, irrespective of the thickness.

Note that it is desirable to carry out degrease processing as the preprocessing of the electroplating, although the cathodic degrease is not carried out. Namely, when the solder film layer 12 is formed by the electroplating method, on the surface of the solder wetting film layer 5 made of niobium (Nb), it is desirable to carry out the degrease processing, other than the cathodic degrease, so that joint failure is not generated.

FIG. 12 shows the result of a case in which chromium (Cr) is selected as the material of the underlayer 7 of the fin member 1, and copper Cu—20 wt % Ni is selected as the material of the surface layer 8.

When chromium (Cr) was selected as the material of the underlayer 7, unlike the case of the niobium (Nb), no joint failure was generated, due to the cathodic degrease which was carried out. Regarding the other point, the same tendency was shown as the case of the niobium (Nb).

Here, it is generally desirable to carry out degreasing, as the preprocessing of the electroplating. This is because if grease, etc, is adhered to the surface to be plated in a manufacturing step, there is a high possibility that the adhesion of grease, etc, becomes a factor of generating defects, etc, in an electroplating film. From this viewpoint, if the underlayer 7 is made of chromium (Cr), this is preferable because degreasing of the underlayer 7 is possible by cathode electrolysis using, for example, alkali solution, even if the grease, etc, is adhered to the underlayer 7.

The underlayer 7 made of niobium (Nb) absorbs hydrogen during cathodic degrease, and an original function as a base can not be fulfilled, and this is considered to be the factor of generating the joint failure due to the cathodic degrease. When the underlayer 7 is made of chromium (Cr), the joint failure does not occur, and the reason therefore is considered that hydrogen absorption does not occur during cathodic degrease in the underlayer 7 made of chromium.

As described above, according to the example of the present invention, it was confirmed that excellent solder joint was achieved by setting the material and the thickness of the solder wetting film layer 5 and the solder film layer 12 to the aforementioned appropriate values.

Note that in the above-described example, explanation is given for a case of using pure tin, an alloy of tin and lead, and an alloy of tin and bismuth, as a base material (main component) of solder. However, the solder base material is not limited thereto.

Also, each kind of specific design specification such as thickness and outer dimension of each substrate of the fin member 1, tube member 2, and tank member 3, is not limited to the structure given in the above-described examples.

Further, for example when only one surface of the fin member 1 is joined to the tube member 2, the solder wetting film layer 5, the solder film layer 12 may be formed on only one surface of the fin substrate 6. It is needless to say that various variations are possible other than the above-described examples.

The present application is based on Japanese Patent Application No. 2009-051974, filed on Mar. 5, 2009, the entire contents of which are hereby incorporated by reference. 

1. A heat exchanger having a structure in which a fin member and a tube member are joined each other, wherein the fin member includes a solder wetting film layer containing copper, in at least a part of a surface of a fin substrate made of aluminum or an alloy mainly composed of aluminum where the fin member and the tube member are joined each other, and the tube member includes a solder film layer made of solder containing tin, in at least a part of a surface of a tube substrate made of copper or an alloy mainly composed of copper where the tube member and the fin member are joined each other, wherein the fin member and the tube member are joined each other, through a diffusion bonding of a copper component of the solder wetting film layer and a tin component of the solder film layer.
 2. A heat exchanger having a structure in which a fin member and a tube member are joined each other, wherein the fin member includes a solder wetting film layer containing copper in at least a part of a surface of a fin substrate made of aluminum or an alloy mainly composed of aluminum where the fin member and the tube member are joined each other, and includes a solder film layer made of solder containing tin on the surface of the solder wetting film layer, and the tube member is made of copper or an alloy mainly composed of copper, wherein the fin member and the tube member are joined each other, through a diffusion bonding of a copper component of the tube member and a tin component of the solder film layer.
 3. The heat exchanger according to claim 1, wherein the solder wetting film layer is formed as a two-layer lamination structure of a underlayer made of niobium or chromium, and a surface layer made of an alloy mainly composed of copper and added with at least one kind of metal of nickel and zinc.
 4. The heat exchanger according to claim 2, wherein the solder wetting film layer is formed as a two-layer lamination structure of a underlayer made of niobium or chromium, and a surface layer made of an alloy mainly composed of copper and added with at least one kind of metal of nickel and zinc.
 5. The heat exchanger according to claim 1, wherein a thickness of the solder wetting film layer is 5 nm or more and 400 nm or less, and a thickness of the solder film layer is 3 μm or more and 100 μm or less.
 6. The heat exchanger according to claim 2, wherein a thickness of the solder wetting layer is 5 nm or more and 400 nm or less, and a thickness of the solder film layer is 3 μm or more and 100 μm or less.
 7. The heat exchanger according to claim 3, wherein a thickness of the solder wetting film layer is 5 nm or more and 400 nm or less, and a thickness of the solder film layer is 3 μm or more and 100 μm or less.
 8. The heat exchanger according to claim 4, wherein a thickness of the solder wetting film layer is 5 nm or more and 400 nm or less, and a thickness of the solder film layer is 3 μm or more and 100 μm or less.
 9. The heat exchanger according to claim 1, wherein the solder film layer is made of pure tin.
 10. The heat exchanger according to claim 2, wherein the solder film layer is made of pure tin.
 11. The heat exchanger according to claim 3, wherein the solder film layer is made of pure tin.
 12. The heat exchanger according to claim 4, wherein the solder film layer is made of pure tin.
 13. The heat exchanger according to claim 3, wherein the solder film layer is made of pure tin, having a thickness of 3 μm or more and 30 μm or less.
 14. The heat exchanger according to claim 4, wherein the solder film layer is made of pure tin, having a thickness of 3 μm or more and 30 μm or less.
 15. The heat exchanger according to claim 3, wherein the underlayer of the solder wetting film layer is made of niobium, and the solder film layer is formed on the surface of the solder wetting film layer not subjected to cathodic degrease, by electroplating.
 16. The heat exchanger according to claim 4, wherein the underlayer of the solder wetting film layer is made of niobium, and the solder film layer is formed on the surface of the solder wetting film layer not subjected to cathodic degrease, by electroplating.
 17. The heat exchanger according to claim 3, wherein the underlayer of the solder wetting film layer is a sputter film made of niobium or chromium, with the underlayer having an internal residual stress of a compression stress or a zero stress, and the surface layer of the solder wetting film layer is the sputter film.
 18. The heat exchanger according to claim 4, wherein the underlayer of the solder wetting film layer is a sputter film made of niobium or chromium, with the underlayer having an internal residual stress of a compression stress or a zero stress, and the surface layer of the solder wetting film layer is a sputter film. 